Generally, a chemical analyser automatically analyses a chemical composition included in blood or urine of a human body, for example. A sample solution and a reagent are dispensed into a reaction cuvette. The chemical analyser measures, as one of biochemistry test arrays, concentration/activity of a substance to be measured or enzyme in the sample solution by measuring amount of penetration of light in order to obtain a change of color tone caused by reaction of a mixed solution of the sample solution and the reagent corresponding to the biochemistry test array.
Moreover, as other biochemistry test arrays, the chemical analyser measures concentration of sodium ion or potassium ion or chlorine ion in a sample solution dispensed into a dilution cup by measuring a change of electromotive force with an ion sensor about a mixed solution of the sample solution and a reagent. In this case, the reagent is used for dilution of the sample solution or adjustment of pH.
Major measurement error which is common to many biochemistry test arrays is caused when the sample solution and the reagent are dispensed and mixed to be uniformed.
There are two dispensing methods of the sample solution and the reagent. One method is a dispensing-first-sample solution method and another is a dispensing-first-reagent method. Both methods have the problems described below, respectively.
In the dispensing-first-sample solution method, the sample solution is dispensed into a container, and subsequently the reagent is dispensed into the container to be mixed with the sample solution.
The dispensing-first-sample solution method is classified into two methods, a non-contacting dispensing method and a contacting dispensing method.
When amount of the sample solution used for each biochemistry test array was large, the non-contacting dispensing method where the sample solution was dispensed into the container from a sample dispensing probe that was away from the container is applied.
However, at the present the amount of the sample solution used for each biochemistry test array is little. Therefore, as the contact dispensing method, the sample solution is dispensed into the container from a sample dispensing probe that is contacting the container has been applied, since the sample solution that should be dispensed into the container is adhered to the outside of the sample dispensing probe or flies in all directions and the sample solution is not dispensed into an appropriate part of the container in the non-contacting dispensing method. The contacting dispensing method is described in Japanese Patent 61-56784 (KOUKOKU) (page 4-5 and FIGS. 4-5).
However, in the contacting dispensing method, the sample solution dispensed into the container does not spread into the container depending on the circumstances where stain remains or a bottom form where the sample dispensing probe contacts the container influences the spread. As described above, the sample solution is not dispensed well.
In order to reduce the problem of the bottom form of the container, high processing accuracy to make the container is required. Especially, in the chemical analyser including a plurality of containers, such as reaction cuvettes, it is difficult to achieve the high processing accuracy. In order to reduce another problem of the remain of the stain, a high flushing capacity is required.
On the other hand, in the dispensing-first-reagent method, the reagent is first dispensed into the container, and the sample solution is dispensed into the container to be mixed with the reagent. The dispensing-first reagent method is described in Japanese Patent Disclose (KOKAI) (page 3).
In the dispensing-first-reagent method, when the sample dispensing probe directly contacts the reagent, or the sample dispensing probe does not contact the reagent but a drop located on a top of the sample dispensing probe contacts a surface of the reagent, the sample solution is poured from the sample dispensing probe into the reagent. The sample solution is not adhered to the outside of the sample dispensing probe or does not fly off, and therefore, the dispensing-first-reagent method is adapted at the present when the amount of the sample solution is little.
The dispensing-first-reagent method needs a more powerful mixing unit than that in the dispensing-first-sample solution method, in order to mix the sample solution and the reagent to be uniformed. However, a speedy measurement or a speedy mixing is required recently, and it is difficult to achieve the required speed even with the powerful mixing unit.
In the chemical analyzer, it is required that the amount of the sample solution used for each biochemistry test array is reduced, and the sample solution is dispensed well.
However, as described above, in the dispensing-first-sample solution method, the bottom form of the container or the remaining stain can be major error factor, and in the dispensing-first-reagent, the powerful mixing unit is required.